Electrical potentiometer



Jan. 23, 1962 s. A. SLENKER ELECTRICAL POTENTIOMETER Filed March 14, 1960 2+ 23 5 FIG. I.

INVENTOR WITNESSES .WmWaoM milm M/w' 7% 5. mm

FIG. 3.

United States Patent 3,018,458 ELECTRICAL POTENTIOMETER Stephen A. Slenker, River Edge Road, Billerlca, Mass.

Filed Mar. 14, 1960, Ser. No. 14,603 Claims. (Cl. 338-143) The present invention relates to a new and novel construction of electrical potentiometer which will decrease the magnitude of undesirable error and noise voltages commonly obtaincd'by such devices when they are used in electrical and electronic systems. Although the principal of this device is specifically adapted to electrical potentiometers it is nevertheless equally practical for use with 7 variable inductors, capacitors, delay lines and any varitinuous multi-turn potentiometer with any number of electrical degrees of rotation but with an extremely small dead space between ends of the potentiometer.

Still another object of the invention is to provide a multi-turn potentiometer without end stops so that it may be driven continuously in one direction by a motor so as to provide a sawtooth voltage waveshape of very low frequency and of lower noise level than would be attainable from a one turn potentiometer.

One important feature of this invention is that the potentiometer can be used in conjunction with a gear train to obtain much finer resolution than the resistance material could yield by using a conventional one turn continuous potentiometer. In fact the resolution is limited only to the number of turns and the basic design can be used for any number of turns. Therefore the basic design is capable of yielding any desired resolution. This feature makes the potentiometer extremely valuable in the use of positional servo systems since its positional accuracy, when used with a gear train, would be many times the accuracy of an ordinary potentiometer.

Generally the novel construction embodied in the electrical potentiometer of the present invention consists of a coiled resistance element in the shape of two coaxial integrally formed helices which are mounted so as to lie on alternate surfaces of a hollow stationary cylindrical support and a contacting device capable of making electrical contact with any portion of the resistance element, the contacting device consisting of a shuttle which rides along the resistance material as a track while making electrical contact between the resistance material and one or both of two contacting strips placed parallel to the longitudinal axis of the helices.

In order to permit the shuttle to travel along the coil member, two apertures are cut through the cylindrical support, providing tunnels through which the shuttle can pass. The contacting strips are shaped so as to permit the shuttle to make electrical contact with both of them while the shuttle is in the exact center of a tunnel and with at least one of them at any other time. The contact strips restrain the shuttle to the same angular position in which they are located in a fashion similar to a trolley wire which restrains a trolley.

The invention will best be understood from a consideration of the following detailed description taken in connection with the accompanying drawingforming a part of this specification, with the understanding that the in- 3,018,458 Patented Jan. 23, 1962 vention is not confined to any strict conformity with the showing the drawing but may be changed and modified so long as such changes and modifications mark no material departure from the salient features of the invention as expressed in the appended claims.

In the drawing:

FIGURE 1 is a side elevation in section of the assem bled potentiometer showing how the shuttle can be transferred from the inner contact strip to the outer contact strip.

FIGURE 2 shows a top elevation partly in section of the stationary part of the potentiometer and also shows some of the positions the shuttle is capable of attaining while traveling along the resistance element.

FIGURE 3 shows an end elevation of the shuttle.

As indicated in the drawings the device consists of a moveable housing 1 and a shaft 2 integrally formed with said housing. Two contact strips 3 and 4 which may be integrally formed are electrically connected together and make a continuous contact with theshuttle 5 While it rides along the resistance material. The resistance material is formed in the shape of two coaxial helical coil members 6 and 7 which are constructed so as to provide a continuous track for the shuttle to follow.

The coil members 6 and 7 are rigidly supported by a cylindrical stationary member 8 which contains two apertures 9 and 10 for the coil members to pass through and which are large enough for the shuttle 5 to pass through.

Although the entire shuttle 5 could be composed of conducting material without departing from the spirit of the invention, the construction shown in FIGURE 3 possesses several advantages. The shuttle frame 11 is composed of an insulating material which is particularly selected so as to give the least abrasive action on the resistance material. The chamfered split washer 12 is kept in electrical contact with the contact strips 3 and 4 by the pressure of spring 13. The wiper 14 makes contact with the resistance material and is electrically attached to the washer 12. The wiper 14 is mechanically connected to the shuttle frame 11 by the screw 15. Point contact on the resistance material is achieved by the dimple 16 in the wiper 14. One of the outside edges of the shuttle housing 11 is chamfered so as to facilitate insertion of the contact strips 3 and 4.

The contact strips 3 and 4 are rigidly imbedded in the moveable housing 2 by force fitting and use of adhesive material. The inner contact strip 4 is soldered into a groove in the axle rod 17 which is anchored into the housing by a locking nut 18. The movable housing and contact strips are free to rotate on the front bearings 19 and rear bearings 20, 21, and 22. The rear side sleeve bearing 20 also serves as an electrical contact to carry the center-tap lead from the inner contact strip 4 to the outer terminal post 23. The electrical ends of the potentiometer are brought out to the terminal posts 24 and 25 through conductors imbedded in the supporting cylinder 8.

The entire assembly is held together by locking nuts 26. The moveable housing is mechanically balanced by means of a counterbalance 27. Tapped holes 28 are provided in the rear of the stationary housing so the potentiometer can be mechanically supported by a suitable bracket.

While the double helical coil member 6 and 7 has been and in the same or in opposite directions While all contacts could be brought out to a third stationary or move able reference through brushes of the type commonly used in motors without departing from the spirit of the invention.

Having thus described my invention what I claim is:

1. In a variable passive element, a coil member composed of two coaxial helices and contact means, part of which is moveable to make electrical contact with the coil member at any point on a line perpendicular to all cross section lines of the passive element, part of said contact means remaining stationary for a Wire to be attached thereto.

2. In a variable passive element with coaxial helical coil members, contact means, part of which is capable of making electrical contact along a line perpendicular to all cross sections of the coil members While said coil members are being rotated continuously in one direction with respect to said contact means and part of which is capable of retaining contact with electrical ends of said coil members, said contact means being capable of continuous rotation in either direction.

3. In a variable passive element, continuous endless coil means, contact means composed of a moveable element which rides along said coil means as a track while retaining electrical contact with a contact strip means, said strip means being rotatable about the axis of said coil means with respect to said coil means and providing a centertap for said coil means.

4. In an electrical potentiometer, a continuous endless coil member whose surface carries an electrical resistance material, contacting means which are composed of contacting strip means which only partially encircle said coil member, and moveable contacting means which make electrical contact between said contacting strip and said resistance material, said moveable contacting means also being capable of making continuous electrical contact between said contacting strip and said resistance material while the potentiometer shaft is being rotated continu ously.

5. In an electrical potentiometer or the like, a continuous endless coil member, contacting means which are composed of contacting strip means which only partially encircle said coil member, and moveable contacting means which make electrical contact between said contacting strip and said resistance material, said moveable contacting means also being capable of making continuous electrical contact between said contacting strip and said resistance material while the potentiometer shaft is being rotated continuously, said contacting strip means being electrically connected to a stationary part of the potentiometer housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,073,948 Schofield Mar. 16, 1937 2,785,261 Roberts Mar. 12, 1957 2,921,283 Luther Jan. 12, 1960 

